Pharmacology

Hyoscyamine is an anticholinergic,
specifically an antimuscarinic, working
by blocking the action of acetylcholine at
parasympathetic sites in smooth muscle, secretory glands and the
CNS; increases cardiac output, dries secretions, and antagonizes
serotonin. At comparable doses, hyoscyamine has 98 per cent of the
anticholinergic
power of atropine and
the other major belladonna-derived drug
scopolamine having 92 per cent of the antimuscarinic potency of
atropine.

Isolation

Hyoscyamine can be extracted from plants of the
Solanaceae
family, notably Datura
stramonium. Empirically it is C17H23NO3. Its structural name is
α-(hydroxymethyl)-, 8-methyl-8-azabicyclo[3.2.1]oct-3-yl ester,
[3(S)-endo]-1αH,5αH-Tropan-3α-ol. Do not crush, chew, or divide the
extended-release capsules, otherwise, an overdose will
result.